Treating chromium-iron alloys



Patented Sept. 16, 1924.

UNITED STATES 1,508,567 PATENT OFFICE.

JOHN H. NEAD, OF MIDDLETOWN, OHIO, ASSIGNOR-TO THE AMERICAN ROLLING MILL COMPANY, OF MIDDLETOWN, OHIO, A CORPORATION OF OHIO.

TREATING CHROMIUM-IRON ALLOYS.

No Drawing.

To all whom it may concewz: r

Be it known that I, JOHN H. N EAD, a citizen of the United States, and a resident of Middletown, in the county of Butler and State of Ohio, have invented certain new and useful Improvements in Treating Chromium-Iron Alloys, of which the following is a full, clear, and exact description.

My invention relates to processes for heat treating the so-called, rustless or stainless chromium iron alloys or steels and pickling thereof, to the end of removing scale formed in the annealing, and the production of a stainless steel strip or sheet which is quite soft, and can be formed up when cold into a great variety of shapes. These stainless steels or iron alloys as made today are formed of various compositions of iron and chromium, with low or high carbon, and with silicon and other additional metals and metalloids.

So far as I am advised the work done in stainless steels, same being usually chromium steels containing substantial quantities of chromium, has been directed toward the production of very hard steel, or steel which would serve to be made into tools, knives and forks, electric heating elements, project-iles, (gun barrels) and metals for use in acid resistance, working at high temperatures and the like. My work is particularly of value in iron chromium alloys having a low carbon content, which can be made so as to anneal to decided softness.

Thus when attempting to place on the market, a mild readily workable sheet or strip of iron chromium alloy material a number of problems present themselves, the solution of one of which forms the basis of this application.

It is necessary in the forming of a mild soft sheet or strip of iron chromium alloys to very thoroughly anneal it, and I have found that when box annealing is resorted to, that the acid resistant qualities of the alloy assert themselves to such an extent that the pickle liquor which it is desirable to use will have little or no effect in raising the scale formed in the hot working of the metal upon being forged or rolled.

(With reference to a typical material, with which my invention will apply, I prefer to use an alloy of chromium, and iron, with as low carbon as possible, and with or without silicon and a small proportion of manganese Serial No. 666,626.

together with possibly a small part of molybdenum, vanadium and the like. The exact proportions of materials do not form any part of this invention, but I may state as a range, within which very acceptable, soft, deep drawing stainless steel sheets can be produced, the following: chromium, around fifteen per cent, of the total ingreclients, with the silicon, if used, around three per cent, or less, carbon two tenths of one per cent, or as low as it is possible to get it, manganese not higher than one half of one per cent. ,The percentages of carbon, silicon, chromium and manganese affect the softness of the material in varying degrees, and the presence of the silicon probably adds to stainlessness, as well as makes it easier to keep down the carbon, and gives good physical qualities for hot working.

The composition of the alloy may vary between wide ranges and the annealing temperatures may be determined for given compositions by the metallurgist.

After a sheet or other piece of material formed on the above or other mild analysis, is reduced from the ingot by forging or (specifically) by hot rolling, it is placed into an annealing box and subjected to heat for the necessary time, at the necessary temperature, to give a soft readily workable product.

The scale left from the hot working is then caused to be loosened from the surface of the sheet by passing the sheet through the cold rolls or even a roller leveler, in such a way as to exert a stretching action on the piece.

This stretching action, I have found will sufficiently tear apart the impermeable coating left from the annealing, so that when proceeding to pickle in the usual manner, in dilute sulphuric acid, or other pickle liquor, the acid can get in under the scale or surface coating, and can attack the metal beneath the scale, and will thus lift or free the scale, so that it washes off or may be brushed off, as in the usual pickling process for steel sheets.

I find, as heretofore stated, that without a stretching of the body beneath the surface coating formed on stainless chromium steel or iron alloys, by box annealing, the surface left from the annealing will not respond at all to a pickling treatment.

After stretching the metal piece, cold rolls and then cold Working the product surficiently to extend the body thereof beneath the coating thereon and finally pickling the product.

2. The treatment of iron chromium alloys or the like material of stainless quality which consists in hot rolling a mass of the metal to form a desired product, then box annealing the product, and then cold rolling the product sufliciently to extend the body thereof beneath the coating thereon and finally pickling the product.

JOHN H. NEAD. 

